gray balance before taking photos and GTI N8

[JimP]

wbassett,

For a projected image in a totally dark room, I would think that you'd want to use a camera setting that is closest to D65. Although D65 isn't the same as 6500 degrees kelvin, 6500 K is close enough. So given that, you'd want to use a manual camera setting that is closest to that. For cameras where you can adjust white balance numerically, 6500 works. But for those who don't and have symbols that represent incandescent, direct sun, shade,etc,....you'd want to use either cloudy bright or something that resembles shade under a tree.

Now, keep in mind that directors will use color tone as a creative tool. Just because I like clean whites doesn't mean that the director choose to tone a scene yellow for warmth or as in the matrix, cool.

When photographing a room with the projector at 6500K, and interior lights at 3200K or if its daylight, 5100 to 6500, you'll have to make a judgement call which element in the picture needs to look right. I would probably choose that the projected image be the most accurate.



When illuminating a room with daylight, things get more complex as day light varies depending on whether its mid day, late day, shady day, etc. You'll probably have to try several settings that are within a close range. from 5,100K to 6500K.

JimP wrote:

It sounds like you're trying to photograph on screen images in a dark room and the home theater room with just ambient lighting without a projected image on the screen. Am I close?

The 1st thing was to check whether GTI N8 paint is truly a "neutral gray" as claimed. That's why I used the whibal card as a comparison because it's certified individually to be neutral gray at 185,185,185. If both are truly neutral, the images taken after a manual white balance should look the same, and whites should be whites, blacks should be black, etc...

The 2nd thing is, I'm trying to come up w/ a way to take pictures of a projected image so that results can be compared from one DIY screen to another.
I think ambient lighting is "coloring" the result you see on-screen, so doing a manual white balance is supposed to take out this side-effect so that we can compare images that we post. The dpreview article is also why I think you need to use something like whibal to set your color balance. Each camera defines "incandescent" differently, and each light source can be a different color. You just can't eyeball it.


ken

[JimP]

ken,

You're right on about the whibal card provided the card is illuminated with the exact same light as the screen...up to a point. Some materials reflect light differently, but what you're doing is as close as you can reasonable get it.

As for photographing a projected image with ambient lighting, tell me if we're talking daylight screaming through windows or room lighting at night and which kind of bulbs.

Maybe if you can provide a link I can tell better what we're talking about.

[wbassett]

kenyee wrote:

The 1st thing was to check whether GTI N8 paint is truly a "neutral gray" as claimed. That's why I used the whibal card as a comparison because it's certified individually to be neutral gray at 185,185,185. If both are truly neutral, the images taken after a manual white balance should look the same, and whites should be whites, blacks should be black, etc...

I can answer this one, it is close, but it isn't dead center D65 neutral. I posted the CIE L*ab data earlier as well as the Yxy and RGB values. It's closer than most of the grays being used for screens in DIY, but for something that is ISO standards I was a bit surprised it wasn't better, as in nailing neutral.

Here is a CIE graph if you're interested.

JimP wrote:

As for photographing a projected image with ambient lighting, tell me if we're talking daylight screaming through windows or room lighting at night and which kind of bulbs.

That's the thing....most people won't have any idea what kind of light it is (I know mine are compact fluorescents), so that's why I mentioned whibal as a common ground that is relatively easy to use (set camera to manual white balance, put card in same lighting, click camera on gray part of card, then take photos of your projector screen). Most people aren't going to fiddle around w/ the color temperature setting of their camera (which you can't do in most P&S used for posting pics) until it looks right :-)

p.s., thanks wbassett...I know the GTI N8 isn't perfectly neutral gray and the photos I took at the start of this thread confirm this. It would be interesting if you could measure a whibal card though ;-) So now I'm wondering if I can take the whibal card, go to Home Depot or Sherwin Williams and ask them to mix up a can of paint that matches it...

[mechman]

JimP wrote:

Hi boys..............can a pro photographer join into the discussion?

To tell you the truth Jim, you the kinda person we've been looking and waiting for! Thanks for joining in! Now I've got read all these posts and get caught up. I'm sure I'll have a couple questions when I'm done!

[mechman]

JimP wrote:

Then you have the flip side of this where you record the scene as neutral as possible or what I do, which is to shoot the scene using the camera raw format and then in photoshop CS2 use the tool in raw converter to white balance the scene. For this to work, you need a known neutral color in the scene such as either a known white or know neutral gray.

This is exactly what I intend to do. Which is why I purchased the Whibal card.

JimP wrote:

From there, for my use, I usually look at the scene and ask myself if the picture looks too warm or cool relative to a reference "shirley" (which is a reference image of various typical scenes and what they look like). As another poster mentioned, mixed lighting will be a problem and you often have to make judgement calls as to which color balance is more attractive.

"Eyeballing it" is what I've been doing so far. But it's tough. Mainly because it's a projected image with varying degrees of ambient light. I take some in darkness and then ramp up the ambient various stages until it's full ambient light.

JimP wrote:

As to photographing an interior scene with consumer grade cameras, the best advice I could give you is to avoid auto white balance and set the camera as follows. If its a room lit with light bulbs, use the tungsten setting on the camera. If your photographing a projected image on the screen in a totally dark room, use the white balance setting for either a heavy overcast day or a clear day under a tree. These setting are usually pretty close to 6500K. Most digital cameras have one or the other.

I have an Olympus E-500. I have used both auto and incandescent(tungsten). They usually end up close to identical - white balance wise.

JimP wrote:

Any questions?

Oh good golly yes! First the question, how do I white balance screen shots using the whibal card? Now a couple screen shots to help with my questions:

Full ambient light shot:



Medium to low ambient light shot:



Dark shot:



What would be the correct procedure for white balancing using the neutral gray card in these shots? Would it be best to set the card down in front of the screen using the ambient light? Or would it be best to take a shot with a white light projected onto the screen and the card on the screen? Of course doing this with each stage of ambient light. Thanks again for piping in Jim! It is appreciated!

[mechman]

wbassett wrote:

This thread is getting to be very interesting.


Interesting because elsewhere when I had a very similar thread going about camera setup and how to take accurate pictures of screen shots, the resident heavy that shows the most of these type of pictures only recommended auto everything.

It is getting good isn't it? I always knew it didn't get enough 'airtime' elsewhere. And now that we have a pro joining it... well I'm happy. I'll leave it at that!

Bill you know as well as I that when that 'resident heavy' talked, we all donned the mudders! Those would be knee boots for working in the muck folks. That guy threw alot of garbage around... still does.

wbassett wrote:

I have a Fuji S3100, not the best camera out there by no means, but also not the worse. I guess for a consumer and taking typical pictures that people shoot, it's a good camera. I have been able to get screen shots that look okay, but none look as good as it does in person, or as good as other people's screenies.

My interest is to learn how to take the best (most accurate) pictures of a screen without any software manipulation. Some people have pulled their images into Photoshop and cleaned them up there, but that leads to a lot of debate on photo manipulation and making the picture look better than it does. Everyone does agree that screenies are eye candy and not an ideal way for people to be judging screen performance, but since the people viewing various screen methods can literally live a thousand miles apart, sometimes a picture is their only 'reference'. (which is why I also like screen specs and data on them)

I'm looking forward to seeing more in this thread and what ideas and tips come up!

Your pics have always looked good to me. And I can say that I've never cleaned up any of my shots. I have varied shutter and aperture settings. ISO is always at 100. Shutter and aperture values are something that I'm going to try and include. Hopefully I'll remember that! When kenyee brought up white balancing elsewhere it was kind of eerie for me. I was actually thinking about it quite a bit but never thought to ask. I'm happy we found a forum with some help available!

[mechman]

JimP wrote:

Fluorescents are a special problem in that they have a discontinuous light distribution and come in many flavors. With that said, there is a specialized flourescent bulb that I use to use to judge color balance in prints from my color darkroom that were suppose to be much more accurate (not the double peak in the reds) and aimed at something like 5200 kelvin.

So I might be of some good to this thread, tell me exactly what you're trying to do and I'll see if I can help.

It sounds like you're trying to photograph on screen images in a dark room and the home theater room with just ambient lighting without a projected image on the screen. Am I close?

You've nailed it on the head! See my post above for questions about how I should accomplish this. And thanks a million again!

[mechman]

kenyee wrote:

It would be interesting if you could measure a whibal card though ;-) So now I'm wondering if I can take the whibal card, go to Home Depot or Sherwin Williams and ask them to mix up a can of paint that matches it...

I'd say give it a shot. What do you have to lose, you only have to buy a quart of it. I may do this myself.